The winner of “Temptation Nation,” the 17th and most recent season of The Biggest Loser, is Roberto Hernandez, a former 348-pound gym teacher from Burbank, Illinois. The show helped the contestant lose a staggering 160 pounds over the course of 13 weeks and awarded him $250,000 for his victory. But if Hernandez hopes to keep the weight off moving forward, it turns out “temptation” will actually have very little to do with his success.

According to a report from The New York Times on Monday, the majority of contestants from The Biggest Loser, which premiered on NBC in 2004, have regained the weight they worked so hard to lose through diet and exercise. In some cases, contestants are even heavier today than when they first appeared on the reality show.

But a new study from Kevin Hall, a scientist at the National Institutes of Health, suggests that obesity is not just a matter of willpower versus craving; rather being chronically overweight has more to do with one’s basic biology. After competing on the show, many contestants saw their resting metabolisms “slow radically” as soon as they returned to normal life.  

“It is frightening and amazing,” Hall, who studied contestants from season eight of The Biggest Loser for six years, told The Times. “I am just blown away.”

One's metabolism often slumps following a diet, but Hall was shocked to find that those of the contestants never fully recovered, becoming even slower over time. The research showed “just how hard the body fights back against weight loss,” The Times wrote. The show's doctor, Robert Huizenga​, suggests that former contestants should exercise nine hours a week and keep an eye on their diets in order to avoid weight gain. 

Since winning The Biggest Loser in 2009, Danny Cahill has steadily gained back more than 100 pounds and has to eat 800 calories less each day than other men his size. Sean Algaier, another contestant on season eight, went from 444 pounds to 289, and is now back to 450. He equates his battle with obesity to a “life sentence.”

“The key point is that you can be on TV, you can lose enormous amounts of weight, you can go on for six years, but you can’t get away from a basic biological reality,” Dr. Michael Schwartz, a professor of medicine at the University of Washington, tells The Times. “As long as you are below your initial weight, your body is going to try to get you back.”

[via New York Times]